Hydrocracking process and catalyst



United States Patent 3,450,626 HY DROCRACKING PROCESS AND CATALYST Carlyle G. Wight and Robert H. Haas, Fullerton, and Rowland C. Hansford, Yorba Linda, Calif., assignors to Union Oil Company of California, Los Angeles, Calif, a corporation of California No Drawing. Filed May 5, 1967, Ser. No. 636,266 Int. Cl. Cg 13/04, 13/06 US. Cl. 208-110 ABSTRACT OF THE DISCLOSURE A novel hydrocracking catalyst is described comprising a siliceous cracking base upon which is deposited a minor proportion of palladium and a minor proportion of an Iron Group metal, preferably nickel, or the oxides and/or sulfides of such metals. This catalyst is particularly useful for the hydrocracking of gas oils to produce a relatively high octane gasoline product of high aromatic content at relatively low temperatures in the substantial absence of sulfur, and with low deactivation rates.

BACKGROUND AND SUMMARY OF INVENTION It is common practice in catalytic hydrocracking to employ a dual-function catalyst comprising a cracking base upon which is deposited a hydrogenating component, usually a Group VIII and/or Group VI-B metal. The main purposes of the hydrogenating component are (1) to promote partial hydrogenation of polycyclic aromatic hydrocarbons and thus overcome their resistance to cracking, and (2) to prevent or inhibit catalyst deactivation by hydrogenating coke precursors, thus reducing coke laydown on the catalyst surfaces. It has been found that the latter function is best served by using highly active hydrogenating metals such as palladium; the Iron Group metals and the Group VI-B metals are much less effective.

Although palladium is highly effective for reducing coke laydown and maintaining catalytic activity, it has been found to be disadvantageous in one respect, viz, in its tendency to promote complete hydrogenation of aromatic hydrocarbons, both polycyclic and monocyclic. As noted above, the partial hydrogenation of polycyclic aromatics is desirable in order to overcome resistance to cracking. But the hydrogenation of monocyclic aromatics, and the complete hydrogenation of all aromatic rings in the polycyclic structures, is undesirable because this leads to the indiscriminate cracking of all ring structures with resultant production of a relatively nonaromatic, low-octane gasoline product. It may also result in the production of undesirable quantities of light pa-raffin hydrocarbons in the C -C range. It would be highly desirable to moderate the hydrogenation activity of palladium so as to render it more selective for the partial hydrogenation of polycyclic aromatics, while still retaining its desirable anti-coking activity.

It is known that the foregoing objective can in large measure be achieved by carrying out the hydrocracking in the presence of sutficient hydrogen sulfide to maintain the palladium in a sulfided state, as disclosed in US. Patent No. 3,132,090. However, these sour hydrocracking systems require expensive plant alloying in order to avoid corrosion problems. It would hence be desirable to provide a sweet hydrocracking system capable of producing the high quality products obtained in the sour systems, whereby the hydrocracking reactors, exchangers, etc., could be more cheaply constructed of low-alloy materials, e.g., low-chrome steel. Also, many commercial low-alloy hydrocracking plants now in operation are designed for relatively high-temperature, sweet operations using Iron Group metal catalysts. In recent years the 12 Claims 3,450,626 Patented June 17, 1969 ice deficiencies of these Iron Group metal catalysts, particularly their relatively high deactivation rate, have become more apparent and it would be desirable to replace the catalyst in such units with a relatively nondeactivating palladium-type catalyst. But the limitations of plant construction have until recently prevented such a substitution because of the unattractive alternatives of either producing a low-octane product in a sweet operation, or encountering prohibitive corrosion rates in a sour operation.

The catalyst of this invention provides a unique solution to all of the foregoing problems. It has now been discovered that the Iron Group metals, particularly nickel, exert a specific modifying eifectupon the hydrogenation activity of palladium, rendering it more selective for the partial hydrogenation of polycyclic aromatic hydrocarbons and coke precursors, as opposed to monocyclic aromatics and polycyclic mono-aromatics. The resulting composite catalyst is found to perform in a sweet hydrocracking system in a manner very similar to a corresponding unmodified palladium catalyst used under the sour conditions described in US. Patent No. 3,132,090. The catalyst may thus be used under sweet conditions in low-alloy reactors to produce a high-octane, aromatic gasoline product over long run lengths characteristic of those obtainable using a pure palladium type catalyst. (For purposes of this invention, sweet hydrocracking systems are defined as those wherein the partial pressure of H S in the gaseous feed to the hydrocracking zone is less than about 0.3 p.s.i., preferably less than 0.2 p.s.i.)

From the foregoing it will be apparent that the principal object of the invention is to provide a modified palladium hydrocracking catalyst which may be utilized more etficiently in the absence of sulfur to produce an aromatic, high-octane gasoline product. Another object is to provide a hydrocracking process which can be operated over long periods of time without catalyst regeneration to produce a constant quality product. A corollary object is to eliminate the need for maintaining sour hydrocracking conditions to obtain high-quality products, and thus to reduce or eliminate expensive alloying in plant construction. Other objectives will be apparent from the more detailed description which follows.

DETAILED DESCRIPTION A. The catalyst The catalysts of this invention are composed essentially of a siliceous cracking base having a cracking activity above that corresponding to a Cat-A cracking activity index of 30, preferably above about 40, upon which is intimately distributed about 0.0 l-3%, preferably 0.05 2% by weight of palladium, and about 0.l20%, preferably 1-10% by weight of one or more of the Iron Group metals, i.e., iron, cobalt or nickel. These active metals may be present in free form, as zeolitic cations of an anionic cracking base, as oxides, as sulfides, or any desired mixed forms. Preferably, both metals are at least partially in sulfided forms under normal hydrocracking conditions. An essential requirement of the catalyst is that both of the hydrogenerating components must be supported upon the same cracking base in a finely divided and intimately commingled state, such as that resulting from impregnation or ion exchange of the base with aqueous solutions of salts of the respective metals. It has been found that the Iron Group metal is substantially ineffective for the present purposes if it is supported on a different substrate than the palladium; in such cases the catalyst is found to display substantially the same characteristics as one containing no Iron Group metal.

Suitable cracking bases for use herein include conventional cogel composites of silica-alumina, silica-magnesia, silica-zirconia, alumina-'boria, silica-titania, silicazirconia-titania, acid treated clays and the like. Acidic metal phosphates such as aluminum phosphate may also be used. Halide promoters such as hydrogen fluoride, boron trifiuoride, or silicon tetrafluoride may also be added to the catalyst. The preferred cracking bases are crystalline zeolites of the molecular sieve type having relatively uniform pore diameters of about 6-14 A., wherein the zeolitic cations are predominantly hydrogen ions and/or polyvalent metal ions. These crystalline zeo lites may be used as the sole cracking base, or they may be mixed with one or more of the amorphous cracking bases such as silica-alumina cogel.

The preferred zeolite cracking bases are those having a relatively high SiO /Al O mole-ratio, between about 3.0 and 12, and even more preferably between about 4 and 8. Suitable zeolites found in nature include for example mordenite, stilbite, heulandite, ferrite, dachiardite, chabazite, erionite, and faujasite. Suitable synthetic zeolites include for examples those of the B, X, Y and L crystal types, or synthetic forms of the natural zeolites noted above, especially synthetic mordenite and faujasite. The preferred zeolites are those having crystal pore diameters between about 8-12 A., wherein the SiO /Al O mole-ratio is between about 3 and 6, and the average crystal size is less than about 10 microns along the major dimension. A prime example of a zeolite falling in this preferred group is synthetic zeolite Y.

The naturally occurring zeolites are normally found in a sodium form, an alkaline earth metal form, or mixed forms. The synthetic zeolites normally are prepared in the sodium form. In any case, for use as a cracking base it is preferred that most or all of the original zeolitic monovalent metals be ion-exchanged out with a polyvalent metal, and/or with an ammonium salt followed by heating to decompose the zeolitic ammonium ions, leaving in their place hydrogen ions and/or exchange sites which have actually been decationized by further removal of water, as described in US. Patent No. 3,130,006:

X (H+).z z 1110 (2) There is some uncertainty as to whether the heating of the ammonium zeolites produces a hydrogen zeolite or a truly decationized zeolite, but it is clear that, (a) hydrogen zeolites are formed upon initial thermal decomposition of'the ammonium zeolite, and (b) if true decationization does occur upon further heating of the hydrogen zeolites, the decationized zeolites also possess desirable catalytic activity. Both of these forms, and the mixed forms are designated herein as being metal-cation-deficient. The preferred cracking bases are those which are at least about 10%, and preferably at least metalcation-deficient, based on the initial ion-exchange capacity. A specifically desirable and stable class of zeolites are those wherein at least about 20% of the ion-exchange capacity is satisfied by hydrogen ions; and at least about 20% by polyvalent metal ions such as magnesium, calcium, zinc, rare earth metals, etc.

Mixed polyvalent metal-hydrogen zeolites may be prepared by ion-exchanging first with an ammonium salt, then partially back-exchanging with a polyvalent metal salt, and then calcining. In some cases, as in the case of synthetic mordenite, the hydrogen forms can be prepared 'by direct acid treatment of the alkali metal zeolites.

The powdered, extruded or pelleted cracking bases described above are suitably impregnated and/or ion-exchanged with aqueous solutions of the desired metal salts either in a single step or in successive steps, followed by draining, drying and converting the metal salts to the desired metal compounds and/or free metals, as for example by calcining in air at elevated temperatures. Suitable metal salts for impregnation purposes include .4 for example the sulfates, nitrates, chlorides, acetates, and the like.

The preferred method of adding the hydrogenating metals, particularly the palladium is by ion-exchange. This is accomplished by digesting the zeolite, preferably in its ammonium form, with an aqueous solution or solutions of a suitable compound of the respective metal wherein the metal is present in a cationic form, as described for example in US. Patent No. 3,236,762. Suitable metal salts for ion exchange purposes include for example nickel nitrate, nickel chloride, nickel sulfate, cobalt nitrate, ferrous chloride, tetrammine palladium chloride, tetrammine palladium nitrate and the like. When the palladium and the Iron Group metal are added separately to the cracking base, it is normally preferable to calcine the catalyst between impregnations and/ or ion-exchangers in order to fix the first added metal on the base so that it will not be removed during the subsequent impregnation and/or ion-exchange step. This is particularly desirable when palladium is the first metal added to the base.

It is normally preferred to employ the catalyst in the form of pellets of about to inch in diameter. To prepare such pellets, the powdered cracking base, either before or after addition of the hydrogenating metals, is first dried to an optimum water content of about 10-30 weight-percent, pelleted with added lubricants, binders, or the like if desired, and calcined at temperatures of e.g. 7001200 F. in order to consolidate and activate the catalyst. This treatment may also etfect decomposition of the zeolitic ammonium ions. In many cases, as where highly active zeolite catalysts are employed, it is desirable to copellet the powdered catalyst with other relatively less active adjuvants, diluents or binders such as activated alumina, silica gel, coprecipitated silica-alumina cogel, magnesia, activated clays and the like, in proportions ranging between about 5% and 50% by weight. These adjuvants may be employed as such, or they may contain a minor proportion of an added hydrogenating metal, e.g. a Group VI-B and/or Group VIII metal.

It is normaly preferred to employ the catalyst in an at least partially sulfided state. Sulfiding may be achieved progressively during the hydrocracking process if the feedstock contains sulfur in amounts greater than about 4 parts per million by weight. Presulfiding may be carried out by treating the dried and/or calcined catalyst with hydrogen sulfide, or mixtures of hydrogen and hydrogen sulfide, at temperatures of e.g. 400-800 F. The sulfided catalysts appear to produce a more highly aromatic product than the completely unsulfided catalyst, but it is characteristic of the present catalyst that they can be maintained in a suitably sulfided state at much lower partial pressures of H 8 than are required in the case of corresponding palladium catalysts which do not contain an Iron Group metal.

B. Feedstocks Feedstocks which may be employed herein include in general any hydrocarbon material boiling above the boiling range of the desired product. For purposes of gasoline production, the preferred feedstocks comprise straight run gas oils, coker distillate gas oils, deasphalted crude oils, cyclic oils derived from catalytic or thermal cracking operations and the like. These feedstocks may be derived from petroleum crude oils, shale oils, tar sand oils, coal hydrogenation products and the like. Specifically, it is preferred to use feedstocks boiling between about 400 and 900 F., having an API gravity of about 20 to 35 and containing at least about 20% by volume of aromatic hydrocarbons.

The process is of maximum benefit in connection with the hydrocracking of feeds which are substantially free of sulfur and nitrogen. Preferably such feeds should contain less than about 200 ppm. of sulfur and less than about 50 p.p.m. of nitrogen. Where the raw feed contains excessive quantities of sulfur and/or nitrogen it is preferably subjected to an initial hydrofining treatment. Hy-

drofining may be carried out under conventional conditions at e.g. 500 to 3000 p.s.i.g., 600 to 850 F., 0.2-5 LHSV, 2,000 to 10,000 s.c.f. of hydrogen per barrel of feed, using conventional hydrofining catalyst comprising a Group VI-B metal oxide and/or sulfide plus an Iron Group metal oxide or sulfide supported upon a substantially non-cracking carrier such as activated alumina. A preferred hydrofining catalyst consists of a presulfided composite of about 20% M00 plus about 2-5 of NiO supported upon an activated alumina carrier containing about 5% by weight of coprecipitated silica gel.

Although the beneficial effect of the Iron Group metal in the palladium hydrocracking catalysts is most apparent in connection with the low-temperature hydrocracking of stream thereof, is suitably treated to remove hydrogen sulfide and thereby maintain the desired H 8 partial pressure in the system. As will be shown hereinafter, the preferred range of hydrogen sulfide partial pressures indicated above is essentially without effect on hydrocracking operations carried out with a palladium catalyst free of Iron Group metals.

Hydrocracking as described above may be carried out in a single pass operation with unconverted oil being diverted to other uses such as diesel fuel or the like, or the unconverted oil may be recycled to extinction, resulting in 100 percent conversion thereof togasoline.

The following examples are cited to illustrate the invention and certain of its critical aspects, but are not to substantially nitrogenand sulfur-free feeds, some increbe construed as limiting in scope: mental increase in product aromaticity is observable in the hydrocracking of feeds containing up to about 0.05 EXAMPLE I weight-percent sulfur and 0.01 weight-percent of nitro- In order to demonstrate the effect of added nickel on gen as compared to the results obtainable with a pallah hydrogenation activity of a Palladium Catalyst, tour dium catalyst free of Iron Group metal. It is hence not indlfiereht catalysts were P p and tested as follows: tended to limit the invention to the use of sulfur-free Catalyst A Was a eopelleted composite of 50% y feedstocks, even though the most dramatic benefits are Weight of a Powdered hydrogen Y Zeolite having b i d h using h feed SiO /Al O mole-ratio of about 4.7, containing about 1.5 Weight-percent Na O and 0.5 Weight-percent of palladium Hydmcmkmg added b ion exchange, and 2) 50% by weight of an Operative hydrocracking conditions contemplated hereamorphous adjuvant consisting of 75% by weight of ac in fall within the following ranges: tivated alumina upon which was impregnated 25 weightpercent of NiO. 1

Catalyst B was a copelleted composite of (1) 50% by 333 ggg weight of a magnesium Y zeolite having a SiO /Al O mole-ratio of about 4.7, to which was added by ion exgfs fffi glii f soii ifiifig 1231533 change 1 Percent y weightof pa m, and 5 ggy i g gjgg fig by wfilghtt if the same alumma-nickel ad uvant employed HiS partial pressure, p.s.i 0-30 .0015-0. 15 n ca a Y Catalyst C was a copelleted composite of (l) 50% by Weight of the powdered magnesium Y zeolite employed The g e cohdftlohs are su 1tab1Y adlusted and in catalyst B, containing 0.5 weight-percent of palladium related to glVe the o s r o Y h P P to Products added by ion exchange followed by calcining, and 14 boiling below t lhltral holllhg Point of the feed Weight-percent of NiO added by impregnation of the caly, oohversloh levels In the range of about 40 cined palladium catalyst with an aqueous nickel nitrate volume-percentile pass, preferably 3M0 volume-percent solution followed b drying, and 2 50% by weight of P P are desirable to obtain a suitable balance activated alumina, the final composition being calcined in tween process economics and selectivity of conversion to air at about 300 the desired P Catalyst D consisted of the same 0.5% palladium- The significance of the Preferred range of hydrogen magnesium-Y zeolite employed in catalyst C, upon which sulfide partial pressures recited above is as follows: The was deposited 15 percent by weight f o by impregna high figure of about pin a Once-through, tion with aqueous nickel nitrate solution. No adjuvant non-recycle operation carried out at 1500 p.s.i.g. and 8000 was employed i hi catalyst, of hydrogen, corresponds to about 220 P-P- Each of the foregoing catalysts was then tested for of sulfur in the feed) is approximate PP limit hydrocracking activity of a hydrofined gas oil (unconwhich can be tolerated in low-alloy reactor systems withverted oil from a previous hydrocracking run in which out encountering prohibitive corrosion rates. The lower the raw feed wa a atalytic cycle oil) boiling between limit of about 0.0015 p.s.i. is a preferred minimum to about 400 and 750 F., having an API gravity of 30.7, maintain the catalyst in an optimum sulfidcd state, resultand containing about 60 Weight percent aromatic hydroingin aproduct of maximum aromaticity. It will be undercarbon, 12 p.p.m. of sulfur, and 2 p.p.m. of nitrogen. stood that in once-through operations, the desired sulfur The hydrocracking conditions were: pressure, 1500 concentration is maintained by adding suitable sulfur comp.s.i.g.; liquid hourly space velocity, 1.0; hydrogen/oil pounds to the feed, or controlling the degree of hydrofinratio, 8,000 s.c.f./b.; temperature adjusted to give about ing to give a hydrocracker feed of suitable sulfur content. 50 volume-percent conversion per pass to 400 F. end In normal recycle operations, the recycle gas, or a slip point gasoline. The results were as follows:

TABLE 1 Catalyst A B C D (asse ts iiiZ i -2i (iii estate (Mums, at A1zOr-25 NiO) (75 AlzOa- 25 NiO) 14% N10) (A1203) 15% N10) Average bed temp. F 528 601 634 644 Vol. percent aromatics in a 23i)" F fraction 1 1 25 26 400 F.+ riaetionnjffllll s 3 51 5a 0gigrglsigoroi1185400 F.

so 72 74 Eateries-13113111313: 3% 73 88 so It is apparent from the foregoing data that catalysts A and B brought about a substantially complete saturation of the gasoline product, notwithstanding that each catalyst contained substantial quantities of nickel deposited on a different substrate than the palladium. The highly aromatic products obtained with catalysts C and D clearly demonstrate the moderating effect of nickel when deposited on the same substrate as the palladium.

EXAMPLE II This example demonstrates that the catalysts of this 10 The run was carried out in once-through operation using 8000 s.c.f./b. of hydrogen and other conditions as set forth in Table 3 below. Product yields and quality were determined during six basic run periods, principally in order to determine the effect of minor variations in sulfur and nitrogen content of the feed. It should be noted that the catalyst was not presulfided for run period A-l, but was presulfided prior to run period A-2. The principal conditions and results of the run were as follows:

TABLE 3 (3+ A+ (3+ 50 p.p m. S 1 Feed A A 93 p.p.m. S 2 50 p.p.m S 1 50 p.p.m. S 2 +20 p.p m. N 3 A-l A-2 A-3 B-l -1 0-2 60-74 100-112 140-160 180-224 240-206 380-424 1.5 1.5 3.0 3.0 3.0 3.0 1,000 1,000 1, 500 1, 500 1, 500 1, 500 550-552 504-507 622-623 638-642 647-648 680-680 -1 0.5 Nil point products 54. 8 60. 9 58. 7 64. 63. 5 64. 0 05-400 F. gasoline yield, vol. percent 62. 2 60. 3 66. 1 62. 3 62. 9 Vol. percent aromatics in C -42O F. gasoline 16 29 31 34 Oct. No. of 07-420" F. gasoline, F1+3 m1. TEL 70. 5 88. 3 00.0 89. 9

1 Average daily temperature increase required to maintain about 60 vol. percent conversion to 420 F. end-point products.

I Added as thiophene. 1 Added as tert butylamine.

invention can be used to produce high quality gasoline at low deactivation rates and with good conversion efficiency to gasoline. The catalyst employed was a copelleted composite of about weight-percent activated alumina and 80 weight-percent by a Y zeolite cracking base upon which was initially deposited 0.5 weight-percent of palladium. This composite was then impregnated with sufficient aqueous nickel nitrate solution to deposit thereon about 9.5 weight-percent of NiO. The Y zeolite cracking base was a mixed magnesium-hydrogen form having an SiO /Al O mole-ratio of about 4.7, containing about 1.4 weight-percent Na O, wherein about 35% of the exchange capacity was satisfied by magnesium ions and about 55% by hydrogen ions. This catalyst was tested for hydrocracking activity over an extended run employing three basic feedstocks described below in Table 2. Feed A was The foregoing data clearly demonstrates that the catalyst maintained its activity very well under a variety of conditions and gave throughout a high quality gasoline product in good yields.

EXAMPLE III TABLE 4 14-!- B Feed A A 93 p.p.rn. S p.p.m. S 50 p.p m. S Run period..- A-l A-2 A-3 13-1 0-1 Catalyst age, h 40-74 -148 -188 196-220 224-250 LHSV 1. 5 1. 5 3.0 3. 0 3. 0 Pressure, p.s.i.g. 1,000 1,000 1, 500 1, 500 1, 500 Teinper atit ire, F.. 550-570 671-689 716-720 740-72135 780-864 -12 0 -80 Vol. percent conversion to 420 F. end-point products 58. 6 55. 8 53. 1 60. 2 64. 6 05-420 F. gasoline yield, vol. percent 63. 0 52.3 42. 4 40.8 Vol. percent aromatics in C7-420 F. gasoline 7 26 29 46 47 Oct. No. of (Jr-420 F. gasoline, F-1+3 n11. TEL 86. 9 87.7 92.9

an unconverted gas oil from a previous hydrocracking run, similar to the feed employed in Example I, while feeds B and C were hydrofined gas oils derived from a blend of catalytic cracking cycle oils and straight run gas oils.

The foregoing data clearly demonstrates that palladium is essential in the catalyst it acceptable deactivation rates and conversion efliciencies are desired. Although the gasoline product was highly aromatic and had a high octane number, the efficiency of conversion to gasoline was very low, and deactivation rates were extremely high.

Results substantially similar to those described in the foregoing examples are obtained when other catalysts within the purview of this invention, and other hydrocracking conditions are employed. It is hence not intended to limit the invention to the details of the examples, but only broadly as defined in the following claims.

We claim:

1. A hydrocracking catalyst composition comprising an active siliceous cracking base upon which i intimately distributed a minor proportion of a palladium hydrogenating component, and a minor proportion of an Iron Group metal hydrogenating component, said hydrogenating components being in the form of free metal, oxides, sulfides, or mixtures thereof.

2. A catalyst composition as defined in claim 1 wherein said cracking base is a crystalline, alumino-silicate zeolite having crystal pore diameters in the range of about 6-14 A., and wherein the zeolitic cations are mainly hydrogen ions, polyvalent metal ions, or mixtures thereof.

3. A catalyst as defined in claim 1 wherein said Iron Group metal is nickel.

4. A catalyst as defined in claim 1 containing from about 0.01-3 weight-percent of palladium, and from about 0.120 weight-percent of nickel.

5. A catalyst as defined in claim 1 wherein said hydrogenating components are added to said cracking base by impregnation or ion exchange from aqueous solution.

6. A process for the hydrocraeking of a mineral oil fraction boiling above the gasoline range to produce therefrom a highly aromatic gasoline product, which comprises contacting said mineral oil fraction plus added hydrogen with a hydrocracking catalyst at elevated temperatures and pressures correlated to effect a substantial conversion to gasoline-boiling-range material, said hydrocracking catalyst comprising an active siliceous cracking base upon which is intimately distributed a minor proportion of a palladium hydrogenating component, and a minor proportion of an Iron Group metal hydrogenating component, said hydrogenating components being in the form of free metal, oxides, sulfides, or mixtures thereof.

7. A process as defined in claim 6 wherein said hydrocracking is carried out substantially in the absence of sulfur.

8. A process as defined in claim 6 wherein said hydrocracking is carried out while maintaining in the hydrocracking zone a partial pressure of hydrogen sulfide between about 0.00l5 and 0.15 p.s.i.

9. A process as defined in claim 8 wherein a minor proportion of ammonia is also maintained in said hydrocracking zone.

10. A process as defined in claim 6 wherein said siliceous cracking base is a Y zeolite wherein the zeolitic cations are mainly hydrogen ions, polyvalent metal ions, or mixtures thereof.

11. A process as defined in claim 6 wherein said Iron Group metal is nickel.

12. A process as defined in claim 6 wherein said Iron Group hydrogenating component and said palladium hydrogenating component are added to said cracking base by impregnation or ion-exchange from aqueous solution.

References Cited UNITED STATES PATENTS 2,120,295 6/1938 Pier et a1. 208108 3,236,762 2/1966 Rabo et a1. 208111 3,297,564 1/1967 Peck et al 208l l1 DELBERT E. GANTZ, Primary Examiner.

A. RIMENS, Assistant Examiner.

US. Cl. X.R. 

